Image display device, image display method, and image display program

ABSTRACT

An image display device having an optical modulation element, which modulates light emitted from a light source according to display information, and displaying a display image based on the display information includes: a unit adjusting the amount of illumination light with respect to light emitted from the light source on the basis of brightness information on the brightness of the display image based on the display information; a color conversion processing unit that performs a color conversion process according to the brightness information with respect to the display information so that the display image can be color-reproduced within a predetermined color space; and a display and driving unit that drives the optical modulation element on the basis of the display information having been subjected to the color conversion process so as to display the display image.

BACKGROUND

1. Technical Field

The present invention relates to an image display device, an imagedisplay method, and an image display program.

2. Related Art

There has been known a conventional image display device which modulateslight emitted from a light source according to display information byusing an optical modulation element and displays a display image basedon the display information. In particular, in order to realize a liquidcrystal display device of which power consumption is low and which isthin, a liquid crystal display device using a liquid crystal light valveas an optical modulation element is under development. In addition, inrecent years, as one type of the liquid crystal display devices, aprojection type display device (projector) or a rear surface projectiontype display device (projection TV), which modulates light emitted froma light source according to display information by using a liquidcrystal light valve and projects the modulated light toward a screenthrough a projection lens in an enlarged manner so as to create aprojection image (display image) on the screen, is widely used.

In the projection type display device or the rear surface projectiontype display device, even though the liquid crystal light valve is usedas an optical modulation element, the range (dynamic range) of thebrightness which can be displayed is narrow due to stray light oroptical leakage occurring in various optical elements forming an opticalsystem, and accordingly, it may be difficult to improve the picturequality. For this reason, the following methods have been proposed as amethod of extending the dynamic range.

For example, as a first method, there has been proposed a method inwhich the amount of illumination light illuminated from a light sourceonto a liquid crystal light valve is controlled (illumination control)according to the average picture level (APL) of display information(picture signal) (for example, refer to JP-A-3-179886).

In addition, for example, as a second method, there has been proposed agray-scale range change processing method (a so-called black and whiteextension processing method) in which the gray-scale range of displayinformation is changed by increasing each pixel value (for example,brightness value or RGB value), corresponding to each pixel, included inthe display information according to brightness information (forexample, brightness value) on the brightness of the display information(picture signal).

In order to create a color projection image, it is general to use aconfiguration in which a plurality of colored light beams emitted from alight source is modulated according to display information,respectively, so as to form each optical image corresponding to each ofthe plurality of colored light beams and then the respective opticalimages are combined.

Here, as a characteristic of a liquid crystal light valve, thetransmittance or reflectance of light has a predetermined limitation. Inaddition, due to the characteristic of the liquid crystal light valve,even when the liquid crystal light valve is driven to realize a blackimage, some light beams leak. For this reason, in the case of a darkimage, for example, even when only an optical image corresponding to anR colored light beam is formed by using a liquid crystal light valve andthe brightness values of optical images corresponding to the other GBcolored light beams are set to zero, the GB colored light beams leakthrough the liquid crystal light valve. As a result, the R coloredoptical image is affected by the other colored light beams and thus thecolor saturation level of the R colored optical image becomes low. Onthe other hand, in the first method, when the amount of illuminationlight is controlled by the illumination control, the amount of the GBcolored light beams leaking through the liquid crystal light valve isreduced to the reduced amount of illumination light. As a result, the Rcolored optical image is not easily affected by the other colored lightbeams and thus the color saturation level of the R colored optical imagebecomes high. That is, the color of a projection image obtained when theamount of illumination light is not adjusted is different from thatobtained when the amount of illumination light is adjusted. For thisreason, when the amount of illumination light is adjusted, there is aproblem in that the color of a projection image is changed.

Furthermore, as another characteristic of a liquid crystal light valve,in many cases, a gray-scale characteristic of the liquid crystal lightvalve is not linear on the chromaticity coordinate and a colorcharacteristic of the liquid crystal light valve at a predeterminedbrightness level is different from that of the liquid crystal lightvalve at another brightness level. For this reason, in the secondmethod, when the gray-scale change process is performed, the colorcharacteristic of the liquid crystal light valve becomes different. Thatis, since the color of a projection image projected through the liquidcrystal light valve becomes different when the gray-scale change processis performed, the above-mentioned problem that the color of theprojection image is changed also occurs.

SUMMARY

An advantage of some aspects of the invention is that it provides animage display device capable of reliably maintaining the color of adisplay image even when the amount of illumination light is adjusted ora gray-scale range change process is performed, an image display method,and an image display program.

According to a first aspect of the invention, an image display devicehaving an optical modulation element, which modulates light emitted froma light source according to display information, and displaying adisplay image based on the display information includes: a unitadjusting the amount of illumination light with respect to light emittedfrom the light source on the basis of brightness information on thebrightness of the display image based on the display information; acolor conversion processing unit that performs a color conversionprocess according to the brightness information with respect to thedisplay information so that the display image can be color-reproducedwithin a predetermined color space; and a display and driving unit thatdrives the optical modulation element on the basis of the displayinformation having been subjected to the color conversion process so asto display the display image.

Here, information on the brightness of a display image based on displayinformation may be used as the brightness information, and it ispossible to adopt information set according to a brightness value ofdisplay information (picture signal), an RGB value, or the like. Inaddition, the brightness information may be created by the image displaydevice on the basis of the display information or may be acquired fromthe outside.

In the invention, the unit adjusting the amount of illumination lightadjusts the amount of illumination light emitted from the light sourceon the basis of the brightness information. In addition, the colorconversion processing unit performs the color conversion processaccording to the brightness information with respect to the displayinformation, that is, a color conversion process according to the amountof illumination light adjusted by the unit adjusting the amount ofillumination light so that the display image can be color-reproducedwithin a predetermined color space. In addition, the display and drivingunit drives the optical modulation element on the basis of the displayinformation having been subjected to the color conversion process so asto display the display image. Thereby, even when the amount ofillumination light is adjusted by the unit adjusting the amount ofillumination light, the color conversion process according to the amountof illumination light with respect to the display information isperformed by the color conversion processing unit. As a result, it ispossible to offset an effect of the adjustment of the amount ofillumination light with respect to the display image and to make thedisplay image color-reproduced within a predetermined color space (astandard color space of sRGB) in both cases in which the amount ofillumination light is adjusted and not adjusted. Thus, it is possible toreliably maintain the color of the display image even when the amount ofillumination light is adjusted.

In the invention, preferably, the image display device further includesa gray-scale range change processing unit that performs a gray-scalerange change process of changing the gray-scale range of the displayinformation by increasing each pixel value, corresponding to each pixel,included in the display information on the basis of the brightnessinformation. In addition, preferably, the display and driving unitdrives the optical modulation element on the basis of the displayinformation having been subjected to the gray-scale range change processand the color conversion process so as to display the display image.

In the invention, for example, when the amount of illumination light isreduced by the gray-scale range change processing unit, it is possibleto perform a gray-scale range change process of extending the gray-scalerange without changing the peak brightness value of the display image.As a result, the range (dynamic range) of the brightness which can bedisplayed can also be extended.

Further, in the invention, as described above, since the colorconversion processing unit performs the color conversion processaccording to the adjusted amount of illumination light, that is, a colorconversion process according to the adjustment of the amount ofillumination light and the gray-scale range change process, with respectto the display information, it is possible to perform the colorconversion process, which corresponds to each color characteristic ofeach optical modulation element (liquid crystal light valve) becomingdifferent due to the gray-scale range change process, with respect tothe display information even when the gray-scale range is changed by thegray-scale range change process of the gray-scale range changeprocessing unit. As a result, it is possible to make the display imagecolor-reproduced within a predetermined color space (for example, astandard color space of sRGB). Thus, even when the amount ofillumination light is adjusted and the gray-scale range is changed, thecolor of the display image can be reliably maintained.

Further, according to a second aspect of the invention, an image displaydevice having an optical modulation element, which modulates lightemitted from a light source according to display information, anddisplaying a display image based on the display information includes: agray-scale range change processing unit that performs a gray-scale rangechange process of changing the gray-scale range of the displayinformation by increasing each pixel value, corresponding to each pixel,included in the display information on the basis of the brightnessinformation on the brightness of the display image based on the displayinformation; a color conversion processing unit that performs a colorconversion process according to the brightness information with respectto the display information so that the display image can becolor-reproduced within a predetermined color space; and a display anddriving unit that drives the optical modulation element on the basis ofthe display information having been subjected to the gray-scale rangechange process and the color conversion process so as to display thedisplay image.

Here, in the same manner as described above, information on thebrightness of a display image based on display information may be usedas the brightness information, and it is possible to adopt informationset according to a brightness value of display information (picturesignal), an RGB value, or the like. In addition, the brightnessinformation may be created by the image display device on the basis ofthe display information or may be acquired from the outside.

In the invention, the gray-scale range change processing unit performsthe gray-scale range change process (a so-called black and whiteextension process) of changing the gray-scale range of the displayinformation by increasing each pixel value, corresponding to each pixel,included in the display information on the basis of the brightnessinformation. In addition, the color conversion processing unit performsa color conversion process according to each color characteristic ofeach optical modulation element (liquid crystal light valve), whichbecomes different when the gray-scale range is changed by the gray-scalechange process of the gray-scale range change processing unit, so thatthe display image can be color-reproduced within a predetermined colorspace. In addition, the display and driving unit drives the opticalmodulation element on the basis of the display information having beensubjected to the gray-scale range change process and the colorconversion process so as to display the display image. Thereby, evenwhen the gray-scale range change process (a so-called black and whiteextension process) is performed by the gray-scale range changeprocessing unit, the color conversion processing unit performs the colorconversion process according to each color characteristic of eachoptical modulation element, which becomes different by the gray-scalerange change process, with respect to the display information. As aresult, it is possible to offset an effect of the change of thegray-scale range with respect to the display image and to make thedisplay image color-reproduced within a predetermined color space (forexample, a standard color space of sRGB) in both cases in which thegray-scale range is changed and not changed. Thus, it is possible toreliably maintain the color of the display image even when thegray-scale range change process is performed.

In the invention, preferably, the image display device further includesa color conversion information storage unit that stores a plurality ofconversion tables corresponding to the brightness information, each ofthe plurality of conversion tables associating each input pixel valuecorresponding to each color with each output pixel value for making thedisplay image color-reproduced within a predetermined color space incorrespondence with each input pixel value. When the color conversionprocessing unit performs the color conversion process, the colorconversion processing unit converts each input pixel value for eachcolor, which corresponds to each pixel, included in the displayinformation into each output pixel value on the basis of one of theplurality of conversion tables corresponding to the brightnessinformation.

Here, it is preferable that a plurality of conversion tables be providedaccording to brightness information. For example, the number ofconversion tables may be equal to the number of processes of changingthe gray-scale range or the number of processes of changing the amountof illumination light according to the brightness information, or thenumber of conversion tables may be less than the number of processes ofchanging the gray-scale range or the number of processes of changing theamount of illumination light according to the brightness information.

In the invention, the color conversion information storage unit storesthe plurality of conversion tables corresponding to the number ofprocesses of changing the amount of illumination light, which isadjusted by the unit adjusting the amount of illumination lightaccording to the brightness information, or the number of processes ofchanging the gray-scale range changed by the gray-scale range changeprocessing unit, each of the plurality of conversion tables beingprovided to associate each input pixel value (each RGB input value)corresponding to each color with each output pixel value (each RGBoutput value) for making the display image color-reproduced within apredetermined color space in correspondence with each input pixel valueand to convert each input pixel value (each RGB input value) for eachcolor, corresponding to each pixel, included in the display informationinto each output pixel value. In addition, when the color conversionprocessing unit performs the color conversion process, the colorconversion processing unit converts each input pixel value into eachoutput pixel value by referring to one of the plurality of conversiontables corresponding to the amount of illumination light adjusted by theunit adjusting the amount of illumination light or the gray-scale rangechanged by the gray-scale range change processing unit. Thereby, aprocessing load at a time when the color conversion process is performedcan be reduced as compared with a case in which, for example, a colorconversion processing unit performs a color conversion process ofcalculating each RGB output value by an operation using a predeterminedcolor conversion function, and as a result, the color conversion processcan be performed quickly.

In the image display device of the invention, preferably, when the colorconversion processing unit performs the color conversion process, thecolor conversion processing unit calculates each output pixel value formaking the display image color-reproduced within a predetermined colorspace by using the brightness information and each input pixel value foreach color, which correspond to each pixel, included in the displayinformation on the basis of a color conversion function using thebrightness information and each input pixel value for each color asconversion parameters.

In the invention, the color conversion processing unit calculates eachoutput pixel value (each RGB output value) for making the display imagecolor-reproduced within a predetermined color space by using thebrightness information corresponding to the display information and eachinput pixel value (each RGB input value) for each color, whichcorresponds to each pixel, included in the display information on thebasis of the color conversion function using the brightness informationand each input pixel value (each RGB input value) for each color asconversion parameters. Thereby, as compared with a case in which, forexample, a color conversion processing unit performs a color conversionprocess of converting each input pixel value into each output pixelvalue by referring to a conversion table, it is possible to reduce theamount of information required for the color conversion process. As aresult, since it is possible to adopt a storage unit having a smallstorage capacity, it is possible to manufacture the image display devicewith a low cost.

In addition, in a configuration in which a matrix operation is performedby using a color conversion function, the circuit configuration of, forexample, the color conversion processing unit in the image displaydevice can be simplified, and accordingly, the power can be saved and alow manufacturing cost can be realized.

Further, in the image display device of the invention, preferably, thecolor conversion processing unit performs the color conversion processwith respect to the display information such that the displayinformation can also be subjected to a gray-scale characteristiccorrection process corresponding to a gray-scale characteristic of theoptical modulation element.

In the invention, since the color conversion processing unit performsthe color conversion process and the gray-scale characteristiccorrection process (y correction process), it is not necessary toprepare a separate processing unit that performs the gray-scalecharacteristic correction. As a result, the circuit configuration of theimage display device can be simplified, and accordingly, the power canbe saved and a low manufacturing cost can be realized.

Furthermore, in the invention, preferably, the image display devicefurther includes a gray-scale characteristic correction processing unitthat performs a gray-scale characteristic correction process, whichcorresponds to a gray-scale characteristic of the optical modulationelement, with respect to the display information. In addition,preferably, the gray-scale characteristic correction processing unitperforms the gray-scale characteristic correction process correspondingto the brightness information.

In the invention, since the gray-scale characteristic correctionprocessing unit performs the gray-scale characteristic correctionprocess (y correction process), which corresponds to the brightnessinformation, with respect to the display information, it is possible toperform the gray-scale characteristic correction process according tothe adjusted amount of illumination light or the changed gray-scalerange even when the amount of illumination light is adjusted or thegray-scale range change process is performed. As a result, the color ofthe display image can be reliably maintained.

In addition, since the gray-scale characteristic correction processingunit is provided separately from the color conversion processing unit,the gray-scale characteristic correction processing unit can have afunction of performing the gray-scale characteristic correction processaccording to gray-scale characteristics of various optical modulationelements as compared with a case in which, for example, the colorconversion process and the gray-scale characteristic correction processare performed at the same time by the color conversion processing unit.As a result, the gray-scale characteristic correction process can bereliably performed according to the gray-scale characteristic of anoptical modulation element.

According to a third aspect of the invention, an image display method ofmodulating light emitted from a light source according to displayinformation and displaying a display image based on the displayinformation includes: adjusting the amount of illumination light withrespect to light emitted from the light source on the basis ofbrightness information on the brightness of the display image based onthe display information; performing a color conversion process accordingto the brightness information with respect to the display information sothat the display image can be color-reproduced within a predeterminedcolor space; and driving the optical modulation element on the basis ofthe display information having been subjected to the color conversionprocess so as to display the display image.

In the invention, since the method is performed by using the imagedisplay device described above, the same effects as in the image displaydevice described above is obtained.

Furthermore, according to a fourth aspect of the invention, an imagedisplay method of modulating light emitted from a light source accordingto display information and displaying a display image based on thedisplay information includes: performing a gray-scale range changeprocess of changing the gray-scale range of the display information byincreasing each pixel value, corresponding to each pixel, included inthe display information on the basis of brightness information on thebrightness of the display image based on the display information;performing a color conversion process according to the brightnessinformation with respect to the display information so that the displayimage can be color-reproduced within a predetermined color space; anddriving the optical modulation element on the basis of the displayinformation having been subjected to the gray-scale range change processand the color conversion process so as to display the display image.

In the invention, since the method is performed by using the imagedisplay device described above, the same effects as in the image displaydevice described above is obtained.

Furthermore, according to a fifth aspect of the invention, an imagedisplay program causes a computer included in an image display device toexecute the image display method described above.

In the invention, since the image display program is executed by thecomputer included in the above-described image display device, the sameeffects as in the image display device described above is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a plan view illustrating an optical system of an image displaydevice according to a first embodiment of the invention.

FIG. 2 is a block diagram illustrating the structure of the imagedisplay device in the first embodiment.

FIG. 3 is a block diagram illustrating the structure of a displayinformation processing unit in the first embodiment.

FIG. 4 is a flow chart explaining an operation of the image displaydevice in the first embodiment.

FIG. 5 is a view illustrating an example of a process in which an imageanalysis processing unit determines the amount of illumination lightaccording to brightness information in the first embodiment.

FIG. 6 is a view illustrating an example of a gray-scale change processof the image analysis processing unit in the first embodiment.

FIG. 7 is a view explaining an example of a characteristic of a liquidcrystal light valve in the first embodiment.

FIG. 8 is a view explaining an example of a characteristic of a liquidcrystal light valve in the first embodiment.

FIG. 9 is a block diagram illustrating the structure of a displayinformation processing unit in a second embodiment.

FIG. 10 is a flow chart explaining an operation of the image displaydevice in the second embodiment.

FIG. 11 is a block diagram illustrating the structure of a displayinformation processing unit in a third embodiment.

FIG. 12 is a flow chart explaining an operation of the image displaydevice in the third embodiment.

FIG. 13 is a view illustrating a modification of each of theembodiments.

FIG. 14 is a view illustrating a modification of each of theembodiments.

DESCRIPTION OF EXEMPLARY EMBODIMENTS First Embodiment

Hereinafter, a first embodiment of the invention will be described withreference to the accompanying drawings.

FIGS. 1 to 3 show a projection type image display device 10 according tothe present embodiment. FIG. 1 is a plan view illustrating an opticalsystem of the image display device 10 in which a liquid crystal lightvalve is used as an optical modulation element and a solid light source(LED (light emitting diode) light source) corresponding to each color ofRGB is used to adjust the amount of illumination light with respect tothe liquid crystal light valve. FIG. 2 is a block diagram illustratingthe structure of the image display device 10. FIG. 3 is a block diagramillustrating the structure of a display information processing unit 12.

Configuration of Optical System of Image Display Device

As shown in FIG. 1, the optical system of the image display device 10 ofthe present embodiment includes a dichroic prism 1, a red solid lightsource 2R, a green solid light source 2G, a blue solid light source 2B,a polarizer 3, a liquid crystal panel 4R, a liquid crystal panel 4G, aliquid crystal panel 4B, and a projection lens 5. In addition, each ofthe liquid crystal panel 4R, 4G, and 4B is mounted with the polarizer 3.

Light emitted from the red solid light source 2R is incident on thedichroic prism 1 through the polarizer 3 and the transmissive liquidcrystal panel 4R, light emitted from the green solid light source 2G isincident on the dichroic prism 1 through the polarizer 3 and thetransmissive liquid crystal panel 4G, and light emitted from the bluesolid light source 2B is incident on the dichroic prism 1 through thepolarizer 3 and the transmissive liquid crystal panel 4B. The liquidcrystal panels 4R, 4G, and 4B form an optical image as a variation of apolarized state according to a picture signal.

The dichroic prism 1 is formed by bonding four triangular prisms. In thedichroic prism 1, a dichroic multi-layered film for red reflection and adichroic multi-layered film for blue reflection are vapor-deposited suchthat inclined surfaces, which are bonded surfaces, of the dichroic prism1 cross each other in an X shape. Primary colors incident on thedichroic prism 1 are combined into one light beam by the dichroic prism1 to be then incident on the projection lens 5. Then, optical imagesformed on the liquid crystal panels 4R, 4G, and 4B are projected onto ascreen 6 by the projection lens 5 in an enlarged manner, and thus aprojection image (display image) is generated on the screen 6.

Further, as shown in FIG. 2, the image display device 10 includes acomputer program which causes various hardware to function as a displayinformation input unit 11, the display information processing unit 12, aunit 13 adjusting the amount of illumination light, display and drivingunits 14R, 14G, and 14B, in addition to the above-mentioned solid lightsources 2R, 2G, and 2B and the liquid crystal panels 4R, 4G, and 4B.

The display information input unit 11 is input with display informationfrom a PC (personal computer), a DVD (digital versatile disk) player, orthe like, performs, for example, a decoding process in a case ofcompressed digital data and performs, for example, an A/D (analog todigital) conversion process in a case of an analog signal, and thensupplies converted image signals corresponding to RGB colors to thedisplay information processing unit 12.

The display information processing unit 12 has a function of determiningthe amount of light to be illuminated onto the liquid crystal lightvalve according to display information of a current frame andtransmitting an adjustment signal according to the amount ofillumination light to the unit 13 adjusting the amount of illuminationlight; and a function of performing a predetermined process (forexample, a color conversion process or a gray-scale characteristiccorrection process) on the display information and transmitting imagedata, which has been subjected to the predetermined process, to each ofthe display and driving units 14R, 14G, and 14B of the liquid crystalpanels 4R, 4G, and 4B corresponding to the respective colors. As shownin FIG. 3, the display information processing unit 12 includes an imageanalysis processing unit 121 serving as a gray-scale range changeprocessing unit, a color conversion processing unit 122, and a colorconversion information storage unit 123.

The image analysis processing unit 121 creates brightness informationwith respect to the brightness of a projection image on the basis of thedisplay information and determines the amount of illumination light tobe illuminated onto the liquid crystal light valve on the basis of thecorresponding brightness information. In addition, the image analysisprocessing unit 121 outputs an adjustment signal according to thedetermined amount of illumination light to the color conversionprocessing unit 122 and the unit 13 adjusting the amount of illuminationlight.

Furthermore, the image analysis processing unit 121 performs agray-scale range change process with respect to the display informationaccording to the determined amount of illumination light and changes thegray scale (dynamic range) used in the liquid crystal light valve. Inaddition, the image analysis processing unit 121 outputs image data,which has been subjected to the gray-scale range change process,according to the display information to the color conversion processingunit 122.

The color conversion processing unit 122 performs a color conversionprocess with respect to display information outputted from the imageanalysis processing unit 121 on the basis of the amount of illuminationlight based on an adjustment signal outputted from the image analysisprocessing unit 121 and color conversion information, which will bedescribed later, stored in the color conversion information storage unit123, and performs a projection image based on the input displayinformation within a predetermined color space (for example, a standardcolor space of sRGB) such that colors can be reproduced. In addition,the color conversion processing unit 122 outputs image data, which hasbeen subjected to the color conversion process, according to the displayinformation to the display and driving units 14R, 14G, and 14B.

The color conversion information storage unit 123 stores colorconversion information for performing the color conversion process inthe color conversion processing unit 122. Specifically, the colorconversion information is composed of a three-dimensional look-up table(hereinafter, referred to as ‘3DLUT’) in which each input pixel value(each RGB input value) corresponding to each color is associated witheach output pixel value (each RGB output value) for making the displayimage color-reproduced within a predetermined color space incorrespondence with each RGB input value and which converts each inputpixel value (each RGB input value) for each color, which corresponds toeach pixel in image data outputted from the image analysis processingunit 121, into each RGB output value. In addition, the color conversioninformation storage unit 123 stores a plurality of 3DLUTs, correspondingto the amount of illumination light, determined according to thebrightness information therein. For example, in the case in which theimage analysis processing unit 121 determines the amount of illuminationlight according to the brightness information in N step, the colorconversion information storage unit 123 stores N 3DLUTs corresponding tothe adjusted amount of illumination light.

The unit 13 adjusting the amount of illumination light controls thesolid light sources 2R, 2G, and 2B corresponding to the respectivecolors and adjusts the amount of illumination light by using a PWM(pulse width modulation) method on the basis of the adjustment signalwith respect to the amount of illumination light output from the displayinformation processing unit 12. That is, the unit 13 adjusting theamount of illumination light controls the amount of light emitted fromthe solid light sources 2R, 2G, and 2B.

The display and driving units 14R, 14G, and 14B generate a drivingsignal on the basis of image data output from the display informationprocessing unit 12 and drive the liquid crystal panels 4R, 4G, and 4B,respectively.

Operation of Image Display Device

Next, an operation of the image display device 10 will be described withreference to the accompanying drawings.

FIG. 4 is a flow chart explaining the operation of the image displaydevice 10.

First, the image analysis processing unit 121 included in the displayinformation processing unit 12 analyzes display information inputtedthrough the display information input unit 11 and determines the amountof light to be illuminated onto a liquid crystal light valve (step S1).

FIG. 5 is a view illustrating an example of a process in which the imageanalysis processing unit 121 determines the amount of illumination lightaccording to the brightness information.

For example, the image analysis processing unit 121 analyzes the inputimage data (display information) and creates histogram showing thenumber of pixels corresponding to the brightness value of the imagedata, as shown an example of FIG. 5. In addition, the image analysisprocessing unit 121 calculates the total brightness value (brightnessinformation) with respect to the entire screen on the basis of thecreated histogram, reads out the amount of illumination lightcorresponding to the total brightness value from, for example, a memory(not shown), and determines the corresponding amount of illuminationlight as an amount of illumination light to be illuminated onto theliquid crystal light valve. In addition, the image analysis processingunit 121 outputs an adjustment signal according to the determined amountof illumination light to the color conversion processing unit 122 andthe unit 13 adjusting the amount of illumination light.

Furthermore, other than the method of determining the amount ofillumination light on the basis of the total brightness value(brightness information), which is the example shown in FIG. 5, it ispossible to use a method in which, for example, a maximum value of abrightness value (RGB value) of input image data is adopted asbrightness information and then the amount of illumination light isdetermined on the basis of the brightness information.

After step S1, the unit 13 adjusting the amount of illumination lightadjusts the amount of illumination light by controlling the solid lightsources 2R, 2G, and 2B corresponding to the respective colors accordingto the adjustment signal output from the image analysis processing unit121 (step S2).

After step S2, the image analysis processing unit 121 performs agray-scale range change process with respect to the input image data(display information) according to the amount of illumination lightdetermined in step S1 (step S3). Then, the image analysis processingunit 121 outputs the image data, which has been subjected to thegray-scale range change process, to the color conversion processing unit122.

FIG. 6 is a view illustrating an example of the gray-scale range changeprocess performed by the image analysis processing unit 121. FIG. 6shows a gray-scale range change process when the amount of illuminationlight is determined according to the histogram shown in FIG. 5.

When the adjustment signal is output to the unit 13 adjusting the amountof illumination light so as to reduce the amount of illumination lightoutput from the solid light sources 2R, 2G, and 2B, as shown in theexample of FIG. 6, the image analysis processing unit 121 extends apixel-side gray-scale range (dynamic range) i1A-i2A, which is forrealizing a brightness range i1-i2 (refer to FIG. 5) based on the inputimage data, to a gray-scale range i1A-i2B within a range in which themaximum value of the amount of light outputted through a pixel of theliquid crystal light valve is not changed and thus a brightness rangei1-i2 having many gray-scale levels is realized. The gray-scale rangechange process makes the gray-scale range widened, and thus a darkportion having a low brightness value can be easily viewed.

After step S3, the color conversion processing unit 122 performs a colorconversion process with respect to the image data outputted from theimage analysis processing unit 121 on the basis of the amount ofillumination light based on the adjustment signal outputted from theimage analysis processing unit 121 and the color conversion informationstored in the color conversion information storage unit 123 (step S4).

Specifically, the color conversion processing unit 122 reads 3DLUTcorresponding to the amount of illumination light (the amount ofillumination light adjusted in step S2) based on the adjustment signaloutput from the image analysis processing unit 121 among the pluralityof 3DLUTs stored in the color conversion information storage unit 123(step S4A).

After step S4A, the color conversion processing unit 122 converts eachRGB input value, which corresponds to each pixel in the image data inputfrom the image analysis processing unit 121, into each RGB output valueby referring to the read 3DLUT (step S4B). Then, the color conversionprocessing unit 122 outputs the image data, having the RGB output valueconverted for each pixel, to each of the display and driving units 14R,14G, and 14B.

After step S4, the display and driving units 14R, 14G, and 14B generatedriving signals corresponding to RGB colors on the basis of the imagedata output from the color conversion processing unit 122, and drive theliquid crystal panels 4R, 4G, and 4B so as to form an optical image oneach of the liquid crystal panels 4R, 4G, and 4B (step S5).

Thereafter, the respective optical images formed on the liquid crystalpanels 4R, 4G, and 4B are combined by the dichroic prism 1 to be a colorimage and the color image is then projected onto the screen 6 by theprojection lens 5 in an enlarge manner, and thus a projection image isgenerated on the screen 6 (step S6).

FIGS. 7 and 8 are views explaining an example of a characteristic of aliquid crystal light valve. FIGS. 7 and 8 show xy chromaticity diagrams,respectively.

Each liquid crystal light valve formed by each of the liquid crystalpanels 4R, 4G, and 4B has the following characteristic.

For example, the liquid crystal light valve has a characteristic inwhich some light beams leak through the liquid crystal light valve evenwhen a black image is realized by setting each RGB output value to zero.For this reason, in the case of a dark image, for example, when an Routput value is 10 and each of GB output values is zero, light leaksthrough the liquid crystal light valve corresponding to each of the GBcolored light beams. As a result, an optical image, having the R coloredlight beam, formed by the liquid crystal light valve corresponding tothe R colored light beam is affected by other colored light beams andthus the color saturation level becomes low. On the other hand, in thecase in which the amount of illumination light is adjusted to reduce theamount of illumination light in step S2, the amount of light leakingthrough each of the liquid crystal light valves corresponding to each ofthe GB colored light beams is reduced due to the effect of the reducedamount of illumination light. As a result, the R colored light beam isnot easily affected by the other colored light beams, and accordingly,the color saturation level becomes high. Specifically, referring to FIG.7, assuming that the chromaticity coordinates corresponding to RGB whichare not affected by the other colored light beams are R0, G0, and B0,respectively, since each optical image corresponding to RGB is easilyaffected by the other colored light beams in a state in which the amountof illumination light is not adjusted, colors corresponding to R0, G0,and B0 change toward a central side so as to reduce the saturationlevel. In addition, in the case in which the amount of illuminationlight is adjusted to reduce the amount of illumination light in step S2,since each optical image corresponding to RGB is not easily affected bythe other colored light beams, the colors corresponding to R0, G0, andB0 do not change toward the central side. As a result, the chromaticitycoordinates are extended outside (that is, toward R0, G0, and B0) andthus the saturation level becomes high. That is, in the case in whichthe amount of illumination light is adjusted, the colors correspondingto R0, G0, and B0 change in the directions indicated by arrows R1, G1,and B1, respectively, and as a result, colors of projection imagesbecome different from each other.

Further, for example, in many cases, the gray-scale characteristic ofthe liquid crystal light valve is not linear on the chromaticitycoordinate and the color characteristic of the liquid crystal lightvalve at a predetermined brightness level is different from that of theliquid crystal light valve at another brightness level. That is, asshown in FIG. 8, assuming that the color characteristic of the liquidcrystal light valve at a predetermined brightness level is acharacteristic C1 in a state in which the amount of illumination lightis not adjusted, when the gray-scale range change process is performedso as to change the gray-scale range in step S3, the colorcharacteristic does not match the characteristic C1 because the RGBvalues of image data output to the display and driving units 14R, 14G,and 14B are different from those in a case in which the amount ofillumination light is not adjusted. For example, the colorcharacteristic becomes a characteristic C2 which is different from thecharacteristic C1.

In the related art, in order that a projection image projected onto thescreen 6 can be color-reproduced in a predetermined color space A0 (forexample, a standard color space of SRGB shown in FIG. 8), a colorconversion process in which the color characteristic C1 of the liquidcrystal light valve at a predetermined brightness level in a state inwhich the amount of illumination light is not adjusted is positionedwithin the predetermined color space A0, for example, a color conversionprocess in which each RGB input value is converted into each RGB outputvalue by referring to one 3DLUT so as to make the characteristic C1positioned within the predetermined color space A0 is performed. In theconventional color conversion process, it is possible to make aprojection image, which is projected onto the screen 6 and of which thecharacteristic C1 is positioned within the predetermined color space A0,color-reproduced within the predetermined color space A0 under the statein which the amount of illumination light is not adjusted. However, inthe conventional color conversion process, there is no counter measureagainst a case in which the colors corresponding to R0, G0, and B0change toward the directions indicated by the arrows R1, G1, and B1,respectively, such that the colors changes as shown in FIG. 7 or a casein which the characteristic C1 changes to the characteristic C2 as shownin FIG. 8 due to the adjustment of the amount of illumination lightperformed in step S2 and the gray-scale range change process performedin step S3 described above. That is, since the projection imageprojected onto the screen 6 cannot be color-reproduced within thepredetermined color space A0, the color of the projection image changes.

Further, the plurality of 3DLUTs stored in the color conversioninformation storage unit 123 is 3DLUTs corresponding to the amount ofillumination light determined by the brightness information as describedabove. That is, the plurality of 3DLUTs stored in the color conversioninformation storage unit 123 is information corresponding to a case inwhich the colors corresponding to R0, G0, and B0 change toward thedirections indicated by the arrows R1, G1, and B1, according to theamount of illumination light such that the colors changes as shown inFIG. 7 or a case in which the characteristic C1 changes to thecharacteristic C2 as shown in FIG. 8. That is, by converting each RGBinput value of input image data into each RGB output value so as tochange the amount of illumination light by referring to 3DLUTcorresponding to the amount of illumination light among the plurality of3DLUTs, even in the case in which the colors corresponding to R0, G0,and B0 change toward the directions indicated by the arrows R1, G1, andB1, such that the colors changes as shown in FIG. 7 or the case in whichthe characteristic C1 changes to the characteristic C2 as shown in FIG.8, the projection image projected onto the screen 6 can becolor-reproduced within the predetermined color space A0.

In addition, the 3DLUT converts each RGB input value, for example, aneight-bit value (one of the values within a range of 0 to 255), of inputimage data, into each RGB output value, for example, a ten-bit value(one of the values within a range of 0 to 1023), according to thegray-scale characteristic of the liquid crystal light valve. That is, inthe present embodiment, the color conversion processing unit 122performs the color conversion process by referring to 3DLUT such that agray-scale characteristic correction (γ characteristic correction) isperformed.

According to the first embodiment described above, since the colorconversion processing unit 122 performs the color conversion process(step S4), which corresponds to the amount of illumination light, forimage data even when the amounts of illumination light beams emittedfrom the red solid light source 2R, the green solid light source 2G, andthe blue solid light source 2B are adjusted, respectively, it ispossible to make the projection image color-reproduced within apredetermined color space A0 by adjusting the amount of illuminationlight so as to offset the effect with respect to the projection image,in both the cases in which the amount of illumination light is adjustedand not adjusted. Accordingly, it is possible to reliably maintain thecolor of the projection image even when the amount of illumination lightis adjusted.

Further, since the color conversion processing unit 122 performs thecolor conversion process, which corresponds to the adjusted amount ofillumination light, for image data, that is, since the color conversionprocess according to the adjustment (step S2) of the amount ofillumination light and the gray-scale range change process (step S3),even when the gray-scale range is changed by the gray-scale range changeprocess, it is possible to perform the color conversion process for theimage data corresponding to each color characteristic (for example, C1or C2) of the liquid crystal light valve, the each color characteristicbecoming changed by the gray-scale range change process. Accordingly,the projection image can be color-reproduced within the predeterminedcolor space A0. As a result, even when the amount of illumination lightis adjusted and the gray-scale range is changed, the color of theprojection image can be reliably maintained.

Here, the color conversion information storage unit 123 stores theplurality of 3DLUTs according to the amount of illumination lightadjusted by the unit 13 adjusting the amount of illumination light, eachof the plurality of 3DLUTs being provided such that each RGB value,which is a pixel value corresponding to each color, is associated witheach RGB output value for making the projection image color-reproducedwithin the predetermined color space A0 in correspondence with each RGBvalue and each RGB input value for each color, which corresponds to eachpixel in image data, is converted into each RGB output value. Inaddition, when the color conversion processing unit 122 performs thecolor conversion process (step S4), the color conversion processing unit122 reads out 3DLUT (step S4A), corresponding to the amount ofillumination light adjusted by the unit 13 adjusting the amount ofillumination light, among the plurality of 3DLUTs, and converts each RGBinput value into each RGB output value by referring to the corresponding3DLUT. Thereby, a processing load at a time when the color conversionprocess is performed can be reduced as compared with a case in which,for example, a color conversion processing unit performs a colorconversion process of calculating each RGB output value by an operationusing a predetermined color conversion function, and as a result, thecolor conversion process can be performed quickly.

Furthermore, since the color conversion processing unit 122 performs thecolor conversion process by referring to 3DLUT such that the gray-scalecharacteristic correction (γ characteristic correction) of the liquidcrystal light valve can also be performed, it is not necessary toprepare a separate processing unit that performs the gray-scalecharacteristic correction. As a result, the circuit configuration of thedisplay information processing unit 12 can be simplified, andaccordingly, the power can be saved and a low manufacturing cost can besaved.

Second Embodiment

Next, a second embodiment of the invention will be described withreference to the accompanying drawings.

FIG. 9 is a block diagram illustrating the configuration of a displayinformation processing unit 12′ in the second embodiment.

The color conversion information storage unit 123 in the firstembodiment stores the plurality of 3DLUTs corresponding to the number ofprocesses of changing the amount of illumination light determined by thebrightness information. In addition, the color conversion processingunit 122 performs the color conversion process by referring to 3DLUT,which corresponds to the amount of illumination light determined by theimage analysis processing unit 121, among the plurality of 3DLUTs.

On the other hand, in the second embodiment, a color conversionprocessing unit 122′ performs a color conversion process of calculatingeach RGB output value of image data by an operation using apredetermined color conversion function on the basis of each RGB inputvalue and the amount of illumination light of inputted image data. Theconfiguration of the second configuration is the same as that of thefirst embodiment except that the color conversion processing unit 122′and a color conversion information storage unit 123′.

The color conversion processing unit 122′ calculates RGB output values(Rout, Gout, Bout) for each color, which correspond to each pixel inimage data to be output to the display and driving units 14R, 14G, and14B by using RGB input values (Rin, Gin, Bin) for each color, whichcorrespond to each pixel in image data output from the image analysisprocessing unit 121 and the amount a of illumination light based on anadjustment signal on the basis of a color conversion function ofequation 1, to be expressed below, in which each input pixel value (RGBinput value (Rin, Gin, Bin) for each color and the amount α ofillumination light determined by the brightness information are used asconversion parameters. In addition, the color conversion processing unit122′ outputs the image data, which has the respective RGB output values(Rout, Gout, Bout) for each color, to the display and driving units 14R,14G, and 14B.R _(out) =f ₁(R _(in) , G _(in) , B _(in), α),G _(out) =f ₂ (R _(in) , G _(in) , B _(in), α),B _(out) =f ₃ (R _(in) , G _(in) , B _(in), α)  Equation 1

For example, equation 1 can be replaced with color conversion functionsto be expressed in equation 2 below.R _(out) =a ₁₁(R _(in) −b ₁₁)^(γ11) +c ₁₁ +a ₁₂ (G _(in) −b ₁₂)^(γ12) +c₁₂+a₁₃ (B _(in) −b ₁₃)^(γ13) +c ₁₃,G _(out) =a ₂₁(R _(in) −b ₂₁)^(γ21) +c ₂₁ +a ₂₂ (G _(in) −b ₂₂)^(γ22) +c₂₂+a₂₃ (B _(in) −b ₂₃)^(γ23) +c ₂₃,B _(out) =a ₃₁(R _(in) −b ₃₁)^(γ31) +c ₃₁ +a ₃₂ (G _(in) −b ₃₂)^(γ32) +c₃₂+a₃₃ (B _(in) −b ₃₃)^(γ33) +c ₃₃  Equation 2

Here, in equation 2, a₁₁, b₁₁, c₁₁, γ₁₁, a₂₁, b₂₁, C₂₁, γ₂₁, a₃₁, b₃₁,c₃₁, and γ₃₁ are adjustment coefficients determined by the amount α ofillumination light and an R input value (Rin) of the image data outputfrom the image analysis processing unit 121. In addition, the colorconversion information storage unit 123′ stores the adjustmentcoefficients as color conversion information. For example, the colorconversion information has a table structure in which each of theadjustment coefficients is associated with the R input value (Rin) andthe amount a of illumination light.

Further, in equation 2, a₁₂, b₁₂, c₁₂, γ₁₂, a₂₂, b₂₂, c₂₂, γ₂₂, a₃₂,b₃₂, c₃₂, and γ₃₂ are adjustment coefficients determined by the amount αof illumination light and a G input value (Gin) of the image data outputfrom the image analysis processing unit 121. In addition, the colorconversion information storage unit 123′ stores the adjustmentcoefficients as color conversion information. For example, the colorconversion information has a table structure in which each of theadjustment coefficients is associated with the G input value (Gin) andthe amount α of illumination light.

Furthermore, in equation 2, a₁₃, b₁₃, c₁₃, γ₁₃, a₂₃, b₂₃, c₂₃, γ₂₃, a₃₃,b₃₃, c₃₃, and γ₃₃ are adjustment coefficients determined by the amount αof illumination light and a B input value (Bin) of the image data outputfrom the image analysis processing unit 121. In addition, the colorconversion information storage unit 123′ stores the adjustmentcoefficients as color conversion information. For example, the colorconversion information has a table structure in which each of theadjustment coefficients is associated with the B input value (Bin) andthe amount α of illumination light.

Next, an operation of the image display device 10 in the secondembodiment will be described with reference to the accompanyingdrawings.

FIG. 10 is a flow chart explaining the operation of the image displaydevice 10 in the second embodiment.

In the second embodiment, as described above, since the configurationsof the color conversion processing unit 122′ and the color conversioninformation storage unit 123′ are different from those of the firstembodiment, the color conversion process (step S4) described in thefirst embodiment is different from that in the second embodiment.Accordingly, only a color conversion process (step S41) will bedescribed below. Other steps S1 to S3, S5, and S6 are the same as thosein the first embodiment, and thus explanation thereof will be omitted.

In step S41, the color conversion processing unit 122′ performs a colorconversion process for the corresponding image data by using the colorconversion functions of equations 1 and 2 described above on the basisof an adjustment signal and image data output from the image analysisprocessing unit 121.

Specifically, the color conversion processing unit 122′ reads out theamount α of illumination light based on the adjustment signal outputfrom the image analysis processing unit 121 and the adjustmentcoefficient corresponding to each RGB input value (Rin, Gin, Bin) of theimage data from the color conversion information storage unit 123′ (stepS41A).

After step S41A, the color conversion processing unit 122′ calculateseach RGB output value (Rout, Gout, Bout) by using the color conversionfunction of equation 2 on the basis of each adjustment coefficient andeach RGB input value (Rin, Gin, Bin) of the image data output from theimage analysis processing unit 121 which have been read out in step S41A(step S41B). In addition, the color conversion processing unit 122′outputs image data, which has the respective RGB output values (Rout,Gout, Bout) calculated for each pixel, to the display and driving units14R, 14G, and 14B.

Furthermore, the color conversion function of equations 1 and 2 convertseach RGB input value (Rin, Gin, Bin) of the inputted image data, forexample, an eight-bit value into each RGB output values (Rout, Gout,Bout), for example, a ten-bit value according to a gray-scalecharacteristic of the liquid crystal light valve. That is, even in thepresent embodiment, the color conversion processing unit 122′ performsthe color conversion process on the basis of equations 1 and 2 describedabove so that the gray-scale characteristic correction (γ characteristiccorrection) of the liquid crystal light valve can also be performed, inthe same manner as in the first embodiment.

The second embodiment has the follow effects other than approximatelythe same effects as in the first embodiment.

The color conversion processing unit 122′ of the second embodimentcalculates each RGB output value for making a projection imagecolor-reproduced within a predetermined color space A0 by using each RGBinput value for each color, which correspond to each pixel in image dataand the amount α of illumination light adjusted by the unit 13 adjustingthe amount of illumination light on the basis of the color conversionfunction in which each pixel value (RGB input value) for each color andthe amount α of illumination light are used as conversion parameters.Thus, as compared with the configuration of the first embodiment inwhich the color conversion processing unit 122 converts each RGB inputvalue into each RGB output value by referring to the corresponding3DLUT, it is possible to reduce the amount of information required forthe color conversion process (step S41). Accordingly, since the colorconversion information storage unit 123′ can be constructed with a smallstorage capacity, the image display device 10 can be manufactured with alow cost.

Third Embodiment

Next, a third embodiment of the invention will be described withreference to the accompanying drawings.

FIG. 11 is a block diagram illustrating the structure of a displayinformation processing unit 12″ in the third embodiment.

The color conversion information storage unit 123 stores the pluralityof 3DLUTs corresponding to the number of processes of changing theamount of illumination light determined by the brightness information.In addition, the color conversion processing unit 122 performs the colorconversion process by referring to 3DLUT, which corresponds to theamount of illumination light determined by the image analysis processingunit 121, among the plurality of 3DLUTs. In addition, the gray-scalecharacteristic correction of the liquid crystal light valve is performedat the same time by the color conversion process of the color conversionprocessing unit 122.

On the other hand, in the third embodiment, a color conversionprocessing unit 122″ performs a color conversion process by performing amatrix operation using a predetermined color conversion function on thebasis of each RGB input value of the input image data and the amount ofillumination light determined by the brightness information. Inaddition, the display information processing unit 12″, includes agray-scale characteristic correction processing unit 124 and agray-scale correction information storage unit 125, and performs agray-scale characteristic correction process separately from the colorconversion process of the color conversion processing unit 122″. Theconfiguration of the third embodiment is the same as that of the firstembodiment except for the color conversion processing unit 122″, thecolor conversion information storage unit 123″, the gray-scalecharacteristic correction processing unit 124, and the gray-scalecorrection information storage unit 125.

The color conversion processing unit 122″ calculates each output pixelvalue (each RGB intermediate output value (R′out, G′out, B′out)) on thebasis of a matrix operation (matrix operation of 3×3) using a colorconversion function of equation 3 in which each RGB input values (Rin,Gin, Bin) for each color, which correspond to each pixel in image dataoutput from the image analysis processing unit 121 is associated withthe amount α of illumination light. In addition, the color conversionprocessing unit 122″ outputs the image data, which has the respectiveRGB intermediate output values (R′out, G′out, B′out) calculated for eachpixel, to the gray-scale characteristic correction processing unit 124.${{Equation}\quad 3{\text{:}\quad\begin{bmatrix}R_{out}^{\prime} \\G_{out}^{\prime} \\B_{out}^{\prime}\end{bmatrix}}} = {\begin{bmatrix}a_{11} & a_{12} & a_{13} \\a_{21} & a_{22} & a_{23} \\a_{31} & a_{32} & a_{33}\end{bmatrix}\begin{bmatrix}R_{in} \\G_{in} \\B_{in}\end{bmatrix}}$

Here, in equation 3, a₁₁, a₂₁, and a₃₁ are adjustment coefficientsdetermined by the amount α of illumination light and an R input value(Rin) of the image data output from the image analysis processing unit121. In addition, the color conversion information storage unit 123″stores the adjustment coefficients as color conversion information. Forexample, the color conversion information has a table structure in whicheach of the adjustment coefficients is associated with the R input value(Rin) and the amount α of illumination light.

Further, in equation 3, a₁₂, a₂₂, and a₃₂ are adjustment coefficientsdetermined by the amount α of illumination light and a G input value(Gin) of the image data output from the image analysis processing unit121. In addition, the color conversion information storage unit 123″stores the adjustment coefficients as color conversion information. Forexample, the color conversion information has a table structure in whicheach of the adjustment coefficients is associated with the G input value(Gin) and the amount α of illumination light.

Furthermore, in equation 3, a₁₃, a₂₃, and a₃₃ are adjustmentcoefficients determined by the amount α of illumination light and a Binput value (Bin) of the image data output from the image analysisprocessing unit 121. In addition, the color conversion informationstorage unit 123″ stores the adjustment coefficients as color conversioninformation. For example, the color conversion information has a tablestructure in which each of the adjustment coefficients is associatedwith the B input value (Bin) and the amount α of illumination light.

The gray-scale characteristic correction processing unit 124 performs agray-scale characteristic correction process with respect to the imagedata output from the color conversion processing unit 122″ on the basisof the amount of illumination light based on an adjustment signal outputfrom the image analysis processing unit 121 and gray-scale correctioninformation, which will be described later, stored in the gray-scalecharacteristic correction processing unit 124.

The gray-scale correction information storage unit 125 stores thegray-scale correction information for performing the gray-scalecharacteristic correction process in the gray-scale characteristiccorrection processing unit 124. Specifically, the gray-scale correctioninformation is composed of a one-dimensional look-up table (hereinafter,referred to as ‘1DLUT’) by which each RGB intermediate value (R′out,G′out, B′out), which corresponds to each pixel in the image data outputfrom the color conversion processing unit 122″, is converted into eachRGB output value (Rout, Gout, Bout) according to the gray-scalecharacteristic of the liquid crystal light valve. In addition, thegray-scale characteristic correction processing unit 124 stores aplurality of 1DLUTs corresponding to the amount of illumination light.For example, in the case in which the image analysis processing unit 121determines the amount of illumination light according to the brightnessinformation in N step, the gray-scale correction information storageunit 125 stores 3N 1DLUTs corresponding to the adjusted amount ofillumination light and each liquid crystal light valve having one of theRGB colors.

Next, an operation of the image display device 10 in the thirdembodiment will be described with reference to the accompanyingdrawings.

FIG. 12 is a flow chart explaining the operation of the image displaydevice 10 in the third embodiment.

In the third embodiment, as described above, since the configurations ofthe color conversion processing unit 122″ and the color conversioninformation storage unit 123″ are different from those of the firstembodiment, that is, the display information processing unit 12″ isprovided with the gray-scale characteristic correction processing unit124 and the gray-scale correction information storage unit 125, a colorconversion process (step S42) is performed instead of the colorconversion process (step S4) described in the first embodiment and agray-scale characteristic correction process (step S7) is performedafter the color conversion process (step S42). Other steps S1 to S3, S5,and S6 are the same as those in the first embodiment, and thusexplanation thereof will be omitted.

In step S42, the color conversion processing unit 122″ performs a colorconversion process for the corresponding image data by using equation 3described above on the basis of an adjustment signal and image dataoutput from the image analysis processing unit 121.

Specifically, the color conversion processing unit 122″ reads out theamount α of illumination light based on the adjustment signal outputfrom the image analysis processing unit 121 and the adjustmentcoefficient corresponding to each RGB input value (Rin, Gin, Bin) of theimage data from the color conversion information storage unit 123″ (stepS42A).

After step S42A, the color conversion processing unit 122″ performs amatrix operation with respect to each RGB input value (Rin, Gin, Bin) ofthe image data output from the image analysis processing unit 121 byusing equation 3 using each adjustment coefficient read in step S42A andthus calculates each RGB intermediate value (R′out, G′out, B′out) (stepS42B). Then, the color conversion processing unit 122″, outputs imagedata, which has the respective RGB intermediate values (R′out, G′out,B′out) calculated for each pixel, to the gray-scale characteristiccorrection processing unit 124.

After step S42, in step S7, the gray-scale characteristic correctionprocessing unit 124 performs a gray-scale characteristic correctionprocess for the image data on the basis of the adjustment signal outputfrom the image analysis processing unit 121, the image data output fromthe color conversion processing unit 122″, and 1DLUT stored in thegray-scale correction information storage unit 125.

Specifically, the gray-scale characteristic correction processing unit124 reads out, for each of the RGB colors, 1DLUT, which corresponds tothe amount of illumination light based on the adjustment signal outputfrom the image analysis processing unit 121, among the plurality of1DLUTs stored in the gray-scale correction information storage unit 125(step S7A).

After step S7A, the gray-scale characteristic correction processing unit124 converts each RGB intermediate value (R′out, G′out, B′out) of theimage data input from the color conversion processing unit 122″ intoeach RGB output value (Rout, Gout, Bout) (step S7B) by referring to eachof the read 1DLUTs. In addition, the gray-scale characteristiccorrection processing unit 124 outputs the image data, which has therespective RGB output values (Rout, Gout, Bout) converted for eachpixel, to the display and driving units 14R, 14G, and 14B.

Further, in the matrix operation using equation 3 described above instep S42, each RGB input value (Rin, Gin, Bin) of the inputted imagedata, for example, an eight-bit value is converted into each eight-bitRGB intermediate value (R′out, G′out, B′out). In addition, by 1DLUT instep S7, each eight-bit RGB intermediate value (R′out, G′out, B′out) isconverted into, for example, each ten-bit RGB output value (Rout, Gout,Bout) according to the gray-scale characteristic of the liquid crystallight valve.

The third embodiment has the follow effects other than approximately thesame effects as in the first and second embodiments.

Specifically, since the color conversion processing unit 122″ performsthe color conversion process of converting each RGB input value intoeach RGB output value in the matrix operation using a color conversionfunction (step S42), it is possible to simplify the circuitconfiguration of the color conversion processing unit 122″. As a result,the power consumed in the image display device 10 can be saved and amanufacturing cost of the image display device 10 can be lowered.

Further, since the gray-scale characteristic correction processing unit124 performs the gray-scale characteristic correction process for theimage data according to the amount of illumination light adjusted by theunit 13 adjusting the amount of illumination light (step S7), it ispossible to reliably maintain the color of a projection image even whenthe amount of illumination light is adjusted.

Furthermore, since the gray-scale characteristic correction processingunit 124 is provided separately from the color conversion processingunit 122″, the gray-scale characteristic correction processing unit 124has a function of performing the gray-scale characteristic correctionprocess according to gray-scale characteristics of various liquidcrystal light valves as compared with the configuration in which thecolor conversion process and the gray-scale characteristic correctionprocess are performed at the same time by each of the color conversionprocessing units 122 and 122′ described in the first and secondembodiments. As a result, the gray-scale characteristic correctionprocess can be reliably performed according to the gray-scalecharacteristics of a liquid crystal light valve.

Here, the gray-scale characteristic correction processing unit 124 readsout, for each of the RGB colors, 1DLUT, which corresponds to the amountof illumination light adjusted by the unit 13 adjusting the amount ofillumination light, among the plurality of 1DLUTs stored in thegray-scale correction information storage unit 125 (step S42A), andconverts each RGB intermediate value into each RGB output value byreferring to each 1DLUT. Thereby, since a processing load at a time whenthe gray-scale characteristic correction process is performed can bereduced as compared to a case in which, for example, the gray-scalecharacteristic correction processing unit 124 performs the gray-scalecharacteristic correction process of calculating each RGB output valueby an operation using a predetermined function, the gray-scalecharacteristic correction process can be performed quickly.

In addition, the invention is not limited to the above-mentionedembodiments, but various modifications and changes can be made withinthe scope and spirit of the invention.

In the embodiments, even though the unit 13 adjusting the amount ofillumination light by controlling the solid light sources 2R, 2G, and 2Bcorresponding to the respective colors has been used as a unit adjustingthe amount of illumination light, the invention is not limited thereto.For example, the following configuration may be adopted.

FIGS. 13 and 14 are views illustrating modifications of the respectiveembodiments. Specifically, FIG. 13 is a plan view illustrating anoptical system when the amount of light is controlled by using a device103 for adjusting the amount of illumination light. FIG. 14 is a blockdiagram illustrating the structure of an image display device 10A whenthe device 103 for adjusting the amount of illumination light is used.

As shown in FIG. 13, the optical system when the device 103 foradjusting the amount of illumination light is used includes a lightsource 100 composed of a gas-emitting light source, such as a metalhalide lamp, a halogen lamp, or a high-pressure mercury lamp, anintegrator lens 101, a polarizing conversion element 102, a device 103for adjusting the amount of illumination light, dichroic mirrors 104 and105, a polarizer 3, liquid crystal panels 4R, 4G, and 4B, condensinglenses 108 and 109, reflectors 110, 111, and 112, a dichroic prism 1,and a projection lens 5.

Light emitted from the light source 100 is transmitted through theoptical system, which includes the integrator lens 101, the polarizingconversion element 102, and the device 103 for adjusting the amount ofillumination light, and is then incident on a color-separation opticalsystem, which includes a dichroic mirror 104 for transmitting red light,a dichroic mirror 105 for transmitting green light, and the reflector112, to be divided into primary light beams having red, green, and bluecolors, respectively. The blue primary light beam is incident on a relayoptical system including a first condensing lens 108, a secondcondensing lens 109, and the two reflectors 110 and 111. The red andgreen primary light beams, which have been transmitted through thecolor-separation optical system, and the blue primary color, which hasbeen transmitted through the relay optical system, are transmittedthrough the polarizer 3 and are then incident on the liquid crystalpanels 4R, 4G, and 4B. The optical path from the light source 100 to theliquid crystal panel 4B is longer than the other optical paths from thelight source 100 to the liquid crystal panels 4R and 4G; however, sincethe two condensing lenses 108 and 109 converge diverging light beams,the light beams can be efficiently transmitted to the blue liquidcrystal panel 4B even though the optical path is long.

In addition, as shown in FIG. 14, the image display device 10A includesa driving unit 113 for adjusting the amount of illumination light so asto drive the device 103 for adjusting the amount of illumination light.

The device 103 for adjusting the amount of illumination light iscomposed of a light restriction mechanism or is made of electrochromicglass, and is disposed at the light emission side of the light source100.

The driving unit 113 for adjusting the amount of illumination lightcontrols the device 103 for adjusting the amount of illumination lightso as to adjust the amount of illumination light on the basis of anadjustment signal of the amount of illumination light supplied from thedisplay information processing unit 12 (12′, 12″).

That is, the device 103 for adjusting the amount of illumination lightand the driving unit 113 for adjusting the amount of illumination lightcorrespond to a unit for adjusting the amount of illumination light.

Further, in the image display device 10A, the driving unit 113 foradjusting the amount of illumination light controls the device 103 foradjusting the amount of illumination light so as to adjust the amount oflight emitted from the light source 100 on the basis of the adjustmentsignal supplied from the display information processing unit 12 (12′,12″) in the process (step S4, S41, and S42) of adjusting the amount ofillumination light described in each of the embodiments. That is, theamount of illumination light emitted from the light source 100 isconstant, and the light is shielded by the device 103 for adjusting theamount of illumination light so as to adjust the amount of illuminationlight supplied to the liquid crystal light valve.

In the configuration described above, since the amount of light emittedfrom the light source 100 is constant and the amount of illuminationlight is adjusted by the device 103 for adjusting the amount ofillumination light, it is possible to effectively adjust the lightsource 100 in which it is difficult to change the amount of lightquickly.

In the embodiments described above, the image analysis processing unit121 analyzes image data so as to create brightness information of theimage data and determines the amount of illumination light according tothe created brightness information; however, the invention is notlimited thereto. For example, a configuration may be adopted in whichbrightness information, which is determined beforehand so as tocorrespond to a predetermined display image, is input from the outsidethrough, for example, the display information input unit 11 and theamount of illumination light is determined according to thecorresponding brightness information. Alternatively, a configuration maybe adopted in which modulated light information related to thepredetermined amount of illumination light, which is determinedbeforehand so as to correspond to a predetermined display image, isinput from the outside through, for example, the display informationinput unit 11 and an adjustment signal according to the correspondingmodulated light information is output to the unit 13 adjusting theamount of illumination light, the color conversion processing units 122,122′, and 122″, the gray-scale characteristic correction processing unit124, or the like.

In the embodiments and the modification, the unit 13 adjusting theamount of illumination light and the driving unit 113 for adjusting theamount of illumination light adjust the amount of illumination lightaccording to the adjustment signal supplied from the display informationprocessing unit 12 (12′, 12″); however, the invention is not limitedthereto. For example, a configuration may be adopted in which the amountof illumination light is gently adjusted with a predetermined timeconstant. In the configuration, it is possible to prevent a projectionimage from blinking due to steep change of the amount of illuminationlight.

In the embodiments and the modification shown in FIGS. 13 and 14, theimage analysis processing unit 121 analyzes image data so as to createthe brightness information and determines the amount of illuminationlight according to the created brightness information, and the unit 13adjusting the amount of illumination light or the driving unit 113 foradjusting the amount of illumination light controls the solid lightsources 2R, 2G, and 2B or the device 103 for adjusting the amount ofillumination light so as to adjust the amount of illumination light;however, the invention is not limited thereto. For example, theinvention may be applied to a configuration in which the amount ofillumination light is not adjusted.

For example, the image analysis processing unit 121 analyzes the imagedata so as to create the brightness information and determines thegray-scale range according to the created brightness information. Then,a gray-scale range change process (a so-called black and white extensionprocess), in which each pixel value corresponding to each pixel of theimage data is increased according to the gray-scale range determined bythe image analysis processing unit 121, is performed so as to change thegray-scale range. In addition, each of the color conversion processingunits 122, 122′, and 122″ performs the color conversion process for theimage data according to the gray-scale range determined by the imageanalysis processing unit 121.

Even in the case in which the amount of illumination light is notadjusted, as described above, the color characteristic of each liquidcrystal light valve is changed due to the gray-scale range changeprocess (a so-called black and white extension process), which changesthe color of the projection image. In the configuration described above,since each of the color conversion processing units 122, 122′, and 122″performs a color conversion process, which corresponds to the colorcharacteristic (for example, C1, C2 (FIG. 8) of each liquid crystallight valve becoming different due to the gray-scale range changeprocess, with respect to the image data, the effect with respect to theprojection image caused by the gray-scale range change process isoffset. As a result, it is possible to make the projection imagecolor-reproduced within a predetermined color space (for example, astandard color space of sRGB) in both the cases in which the amount ofillumination light is adjusted and not adjusted.

In the first embodiment, the color conversion information storage unit123 stores ‘n’ 3DLUTs in correspondence with the number N, which is thenumber of processes of changing the amount of illumination light;however, the invention is not limited thereto. For example, it ispossible to adopt a configuration in which a smaller number of 3DLUTsthan the number N are stored beforehand in the color conversioninformation storage unit 123 and an insufficient part is calculated byan interpolation process.

Further, in the same manner, in the third embodiment, the gray-scalecorrection information storage unit 125 stores N 1DLUTs for each of theRGB colors in correspondence with the entire steps of adjusting theamount of illumination light; however, the invention is not limitedthereto. For example, it is possible to adopt a configuration in which asmaller number of 1DLUTs than the number N are stored beforehand in thecolor conversion information storage unit 123 for each of the RGB colorsand an insufficient part is calculated by an interpolation process.

Furthermore, the invention is not limited to the configuration in whichthe gray-scale characteristic correction process is performed byreferring to 1DLUT, but may be applied to a configuration in which thegray-scale characteristic correction process is performed by changing acoefficient according to the amount of illumination light adjusted bythe unit 13 adjusting the amount of illumination light so as to performan operation using a function approximation.

In the embodiments described above, the image analysis processing unit121 analyzes image data and determines the amount of illumination lightaccording to the brightness information and then the unit 13 adjustingthe amount of illumination light uniformly adjusts the amount ofillumination light of each of the solid light sources 2R, 2G, and 2B;however, the invention is not limited thereto. For example, the imageanalysis processing unit 121 analyzes the image data and creates thebrightness information for each of the RGB colors. In addition, theimage analysis processing unit 121 determines the amount of illuminationlight for independently adjusting the amount of illumination light ofeach of the solid light sources 2R, 2G, and 2B on the basis of thebrightness information for each of the RGB colors created by the imageanalysis processing unit 121. Then, in steps S2 and S3, the process ofadjusting the amount of illumination light and the gray-scale rangechange process are performed for each of the RGB colors according to thedetermined amount of illumination light.

Here, in the first embodiment, when the combination number of processesof changing the amount of illumination light corresponding to the RGBcolors is N N³ or less DLUTs are stored in the color conversioninformation storage unit 123 in correspondence with the number N³, whichis the combination number of processes of changing the amount ofillumination light corresponding to the RGB colors. In addition, in stepS4, the color conversion processing unit 122 reads out 3DLUTcorresponding to the combination of processes of changing the amount ofillumination light corresponding to the RGB colors, and performs thecolor conversion process for the image data on the basis of thecorresponding 3DLUT.

Furthermore, in the second embodiment, in step S41, the color conversionprocessing unit 122′ calculates each RGB output value (Rout, Gout, Bout)for each color, which correspond to each pixel in image data to beoutput to the display and driving units 14R, 14G, and 14B by using eachRGB input value (Rin, Gin, Bin) for each color, which correspond to eachpixel in image data output from the image analysis processing unit 121and each of the amounts αR, αG, and αB of illumination light based onthe adjustment signal on the basis of a color conversion function ofequation 4, to be expressed below, in which each input pixel value (RGBinput value (Rin, Gin, Bin) for each color and each of the amounts αR,αG, and αB of illumination light determined by the brightnessinformation are used as conversion parameters.R _(out) =f ₁(R _(in) , G _(in) , B _(in), α_(R)),G _(out) =f ₂(R _(in) , G _(in) , B _(in), α_(G))B _(out) =f ₃(R _(in) , G _(in) , B _(in), α_(B))  Equation 4

In the first and second embodiments described above, even though thecolor conversion processing units 122 and 122′ perform the colorconversion process and the gray-scale characteristic correction processat the same time, the invention is not limited thereto. For example, inthe same manner as in the third embodiment, it is possible to adopt theconfiguration in which a separate gray-scale characteristic correctionprocessing unit for performing the gray-scale characteristic correctionprocess may be prepared.

Further, in the second and third embodiments described above, eventhough the color conversion information storage units 123′ and 123″store all of the adjustment coefficients, the invention is not limitedthereto. For example, it is possible to adopt a configuration in whichonly an adjustment coefficient corresponding to a predetermined amountof illumination light is stored and other adjustment coefficients arecalculated by an operation.

Furthermore, even though the projection type image display device hasbeen described as an example of an image display device in theembodiments, the invention can be applied to, for example, a rearsurface projection type display device or a direct view type liquidcrystal display device using a backlight. In addition, the backlightused in the direct view type liquid crystal display device may bedisposed, for example, at the rear side of an optical path of a liquidcrystal light valve and be configured such that a plurality of longbar-shaped hot cathode fluorescent lamps (HCFL), each of which ahorizontal width is longer than a vertical width thereof, is arranged inthe vertical direction from the upper side of a screen and then theplurality of hot cathode fluorescent lamps is sequentially lighted sothat the corresponding illuminations are scanned in the verticaldirection.

Furthermore, even though the liquid crystal light valve has beendescribed as an example of an optical modulation element in theembodiments, the invention is not limited thereto. For example, a DMD(digital micromirror device) or a reflective liquid crystal panel (LCOS:liquid crystal on silicon) may be used as the optical modulationelement.

In addition, even though the best mode or the like for performing theinvention has been described above, the invention is not limitedthereto. In other words, while the invention has been described withreference to the exemplary embodiments thereof, it should be understoodthat the invention is not limited to those embodiments but variouschanges and modifications with respect to the shape, a material, and thenumber of components could be made by one skilled in the art withoutdeparting from the spirit or scope of the invention.

Therefore, the material, construction, etc. in each of the embodimentsare only illustrative to make the invention easily understood and do notrestrict the invention, and a name of a component excluding a part ofthe shape or material thereof or a name of the component excluding allof shape or material thereof is also included in the invention.

Since the image display device of the invention can reliably maintainthe color of a display image even when the amount of illumination lightis adjusted or the gray-scale range change process is performed, theimage display device of the invention can be used as an image displaydevice for the purpose of a presentation or a home theater.

The entire disclosure of Japanese Patent Application No.2005-105751,filed Apr. 1, 2005 is expressly incorporated by reference herein.

1. An image display device having an optical modulation element, whichmodulates light emitted from a light source according to displayinformation, and displaying a display image based on the displayinformation, the image display device comprising: a unit adjusting theamount of illumination light with respect to light emitted from thelight source on the basis of brightness information on the brightness ofthe display image based on the display information; a color conversionprocessing unit that performs a color conversion process according tothe brightness information with respect to the display information sothat the display image can be color-reproduced within a predeterminedcolor space; and a display and driving unit that drives the opticalmodulation element on the basis of the display information having beensubjected to the color conversion process so as to display the displayimage.
 2. The image display device according to claim 1, furthercomprising: a gray-scale range change processing unit that performs agray-scale range change process of changing the gray-scale range of thedisplay information by increasing each pixel value, corresponding toeach pixel, included in the display information on the basis of thebrightness information, wherein the display and driving unit drives theoptical modulation element on the basis of the display informationhaving been subjected to the gray-scale range change process and thecolor conversion process so as to display the display image.
 3. An imagedisplay device having an optical modulation element, which modulateslight emitted from a light source according to display information, anddisplaying a display image based on the display information, the imagedisplay device comprising: a gray-scale range change processing unitthat performs a gray-scale range change process of changing thegray-scale range of the display information by increasing each pixelvalue, corresponding to each pixel, included in the display informationon the basis of the brightness information on the brightness of thedisplay image based on the display information; a color conversionprocessing unit that performs a color conversion process according tothe brightness information with respect to the display information sothat the display image can be color-reproduced within a predeterminedcolor space; and a display and driving unit that drives the opticalmodulation element on the basis of the display information having beensubjected to the gray-scale range change process and the colorconversion process so as to display the display image.
 4. The imagedisplay device according to claim 1, further comprising: a colorconversion information storage unit that stores a plurality ofconversion tables corresponding to the brightness information, each ofthe plurality of conversion tables associating each input pixel valuecorresponding to each color with each output pixel value for making thedisplay image color-reproduced within a predetermined color space incorrespondence with each input pixel value, wherein, when the colorconversion processing unit performs the color conversion process, thecolor conversion processing unit converts each input pixel value foreach color, which corresponds to each pixel, included in the displayinformation into each output pixel value on the basis of one of theplurality of conversion tables corresponding to the brightnessinformation.
 5. The image display device according to claim 1, wherein,when the color conversion processing unit performs the color conversionprocess, the color conversion processing unit calculates each outputpixel value for making the display image color-reproduced within apredetermined color space by using the brightness information and eachinput pixel value for each color, which correspond to each pixel,included in the display information on the basis of a color conversionfunction using the brightness information and each input pixel value foreach color as conversion parameters.
 6. The image display deviceaccording to claim 1, wherein the color conversion processing unitperforms the color conversion process with respect to the displayinformation such that the display information can also be subjected to agray-scale characteristic correction process corresponding to agray-scale characteristic of the optical modulation element.
 7. Theimage display device according to claim 1, further comprising: agray-scale characteristic correction processing unit that performs agray-scale characteristic correction process, which corresponds to agray-scale characteristic of the optical modulation element, withrespect to the display information, wherein the gray-scalecharacteristic correction processing unit performs the gray-scalecharacteristic correction process corresponding to the brightnessinformation.